fix error at insert_node when parent_id has been ommitted

lib/radiator/outline.ex

@@ -80,20 +80,22 @@ defmodule Radiator.Outline do
       prev_id = attrs["prev_id"]
       parent_id = attrs["parent_id"]
       episode_id = attrs["episode_id"]
+
+      prev_node = NodeRepository.get_node_if(prev_id)
+      parent_node = find_parent_node(prev_node, parent_id)
+
       # find Node which has been previously connected to prev_node
       next_node =
         Node
         |> where(episode_id: ^episode_id)
         |> where_prev_node_equals(prev_id)
-        |> where_parent_node_equals(parent_id)
+        |> where_parent_node_equals(get_node_id(parent_node))
         |> Repo.one()
 
-      with prev_node <- NodeRepository.get_node_if(prev_id),
-           parent_node <- find_parent_node(prev_node, parent_id),
-           true <- parent_and_prev_consistent?(parent_node, prev_node),
+      with true <- parent_and_prev_consistent?(parent_node, prev_node),
            true <- episode_valid?(episode_id, parent_node, prev_node),
            {:ok, node} <- NodeRepository.create_node(set_parent_id_if(attrs, parent_node)),
-           {:ok, _node_to_move} <- move_node_if(next_node, parent_id, node.uuid) do
+           {:ok, _node_to_move} <- move_node_if(next_node, get_node_id(parent_node), node.uuid) do
         %NodeRepoResult{node: node, next_id: get_node_id(next_node)}
       else
         false ->

test/radiator/outline_test.exs

@@ -187,6 +187,21 @@ defmodule Radiator.OutlineTest do
       assert new_node.prev_id == nested_node_1.uuid
     end
 
+    test "the next node - if existing - changes its prev_id and gets returned", %{
+      node_2: node_2,
+      node_3: node_3
+    } do
+      node_attrs = %{
+        "content" => "new node",
+        "episode_id" => node_2.episode_id,
+        "prev_id" => node_2.uuid
+      }
+
+      {:ok, %{next_id: next_id, node: new_node}} = Outline.insert_node(node_attrs)
+      assert node_3.uuid == next_id
+      assert NodeRepository.get_node!(node_3.uuid).prev_id == new_node.uuid
+    end
+
     test "if prev_id has been given the parent_id can be omitted", %{
       node_3: node_3,
       nested_node_1: nested_node_1